Evolution of texture and microstructure during high strain rate torsion of aluminium zinc magnesium copper alloy

Abstract

Deformation behaviour of aluminium-zinc-magnesium-copper alloy AA 7075 was investigated at high strain rate using Split Hopkinson Torsional Bar (SHTB). Cylindrical AA 7075 specimens were deformed at different angles of twist, giving rise to strain rate ranging from 700s−1 to 2000s−1. Comprehensive microstructural and textural investigation was carried out using electron back scatter diffraction (EBSD), X-ray line profile analysis and bulk texture measurement using X-rays for all the deformed samples. The high strain rate torsion tested samples showed a characteristic torsion texture for face centre cubic materials with a dominant A {11̅1̅}<110>/{1̅11}<1̅1̅0> component and the overall texture weakened with increase in strain rate and strain. Intragranular misorientation parameters like local average misorientation and grain orientation spread indicated occurrence of dynamic recovery in the sample deformed at the highest strain rate which was characterized by the maximum fraction of low angle grain boundaries. Microstructural parameters determined from X-ray diffraction using modified Williamson-Hall and Variance method further corroborated these results indicating the onset of dynamic recovery at the highest strain rate.